This invention relates generally to paperboard cartons. More particularly, this invention relates to a system and method for making a paperboard carton.
The converting of paperboard into carton blanks, and then into folding cartons, can be accomplished with a variety of paperboard substrates depending upon the needs and/or cost constraints of the manufacturer as dictated by the end-user. For example, beverage cartons for soft drink and beer cans traditionally utilize a clay-coated paper kraft board. Other consumable or non-durable retail consumer goods, however, are packaged in a wide variety of substrates including, but not limited to, clay coated recycled paperboard, solid bleached sulfate paperboard, poly-coated solid bleached sulfate paperboard, foil-coated paperboard (recycled and virgin), film coated paperboard (such as metalized polyesters laminated to paperboard substrates), wax-coated paperboard, and various other kinds of paperboard that have been treated, e.g., with special additives such as grease inhibitors.
In addition to the coatings and laminations that are part of the raw paperboard roll stock when it arrives at a carton manufacturer""s plant, the manufacturer often further alters one or more characteristics of the board during the carton blank manufacturing process. Typical alterations of the surface of the paperboard include the graphics, and/or product information on the carton blanks. Different inks and coatings, of course, produce different surface characteristics on the paperboard.
The manufacturing process for folding cartons also includes an operation known as xe2x80x9cfinishingxe2x80x9d whereby a printed and/or coated carton blank is folded and glued on a machine referred to in the industry as a xe2x80x9cfolder-gluer.xe2x80x9d Depending upon the surface characteristics of the particular carton blank being folded and glued, a glue must be selected which provides the best combination of adhesive strength and low cost. Typically, carton manufacturers utilize inexpensive cold-resin glues, not unlike what might be found in a bottle of Elmer""s(copyright) glue. With ordinary clay-coated paperboard, cold-resin glues usually penetrate the clay coating and ink to impregnate the fibrous mass of the carton blank. The result is a bond sufficient to xe2x80x9cpull fiberxe2x80x9d, i.e., sufficient to tear the paperboard of one or both glued together panels of the carton blank, when the carton is stressed or opened at the manufacturer""s seam.
Problems occur, however, when the glue panels of a carton blank are treated with special inks, or covered with special foils, coatings, etc., which inhibit and/or prevent a cold-resin glue from bonding to the paperboard panels sufficient to xe2x80x9cpull fiber.xe2x80x9d In these cases, carton manufacturers typically utilize costlier means to achieve an adequate bond. For example, special poly-glues and/or hot melt glues are often used in such difficult applications. In some cases, often with foilized substrates, manufacturers actually will scuff the carton blank with an abrasive element (e.g., sandpaper) at the point of contact where the board meets the glue in order to achieve an adequate bond. In other cases, manufacturers will flame-treat the carton blanks on the folder-gluer to change the surface tension of the substrate and allow for a better glue bond.
Simply stated, it is often problematic to glue carton blanks inexpensively, if at all, with cold-resin glues when the paperboard from which the carton blank is made has been coated and/or treated with agents that prevent the glue from creating a commercially adequate bond between glued together glue panels or flaps of the carton blank. In other words, if the glue does not penetrate the carton blank""s coating layer, the result is a surface bond which is usually inadequate to hold the carton together during subsequent downstream operations, such as filling the carton with product, distributing the carton to a retailer, and retailing the carton to the end user of the product.
Therefore, it has been an objective of this invention to provide a system and method for manufacturing a paperboard carton utilizing cold-resin glues or other economical standard adhesives in order to permit an effective bond between the carton blank""s glue panels and/or flaps even when the underlying substrate of the carton blank has been coated and/or treated with agents that ordinarily would prevent that glue from coming into contact with the fibers of the paperboard carton blank.
A still further objective of this invention has been to provide such a method and system which can be efficiently and economically utilized in the commercial production of paperboard cartons without detrimentally impacting the appearance or utility of the resulting cartons or the production speed of the cartons.
These and other objectives have been attained by a method and system whereby the paperboard carton blank is etched with a laser beam to allow for adequate adhesion of the carton blank""s glue panels and/or flaps by cold-resin and/or other standard glues. In a presently preferred embodiment according to this invention, a supply of paperboard carton blanks is serially fed on a conveyor or the like through a work station. Each of the carton blanks has at least one glue panel or flap on which glue will be applied to erect the carton. The carton blank""s glue panel initially has a coating layer which prevents or inhibits standard glues from adhering to the fibers of the paperboard to provide an adequate, commercially acceptable bond. According to this invention, a laser beam is directed onto the glue panel on each of the carton blanks so as to remove at least a portion of the coating layer on each glue panel. This allows a cold-resin or other standard glue to be effectively applied to the laser-etched glue panel, and the carton blank subsequently to be successfully folded and glued into a carton configuration. Each carton blank""s laser-etched glue panel enables the cold-resin glue to bond with the fibers of the paperboard so as to produce an adequate bond to hold the carton together during subsequent downstream operations such as filling the carton with product, and distribution of the carton to a retailer and, ultimately, to a retail purchaser.
Additionally, the presently preferred embodiment of the invention includes dispersing the laser beam through an optical lens or other mechanism in order to direct the laser beam over a desired area of the glue panel for removal of the unwanted coating layer in that area. Moreover, the intensity of the laser beam is controlled electronically as a function of the speed of the carton blanks through the work station, the dispersion of the laser beam, and the depth of the etching desired (i.e., the amount of the unwanted coating layer to be removed on the glue panels of the carton blanks being processed).
As a result of the laser-etching method and system according to this invention, carton blanks can be glued inexpensively with cold-resin or other standard glues even when the paperboard carton blank has been coated and/or treated with a coating layer or other agents that typically prevent such glues from coming into contact with the paperboard fibers of the carton blank. After the glue panel of the carton blank has been etched with the laser, the cold-resin glue is applied to that glue panel, and it tends to impregnate to some extent the paperboard so as to provide an effective adhesive bond after gluing the carton blank into carton configuration. Moreover, this invention can be integrated into a production process for manufacturing cartons from carton blanks by controlling the intensity of the laser beam as a function of the speed of the carton blanks transported through the process, the dispersion of the laser beam, and the desired etching depth on the glue panel of the carton blank, all without detrimentally impacting cost or efficiency of the process.